Oil-water mixtures are generated as a result of various activities, and a major source of such mixtures is industrial activity. For a number of reasons, it is desirable to separate the oil from such mixtures. Environmentally, it is desirable to limit the amount of pollution resulting from the discharge of such mixtures resulting from the sites of such industrial activity; it is preferable to recycle and reuse the oil and water components of the mixtures. Economically, it is often desirable to continue to utilize a solution in which an oil becomes a contaminant, as such solutions typically contain a number of additives which are expensive. It is also desirable to remove an oil contaminant so that a particular industrial process may proceed under conditions which are as clean and uncontaminated as possible, thus improving both the manufacturing process and workplace health and safety.
For example, many machine parts or heat treated parts are washed in parts washing tanks, resulting in the washing solution becoming contaminated with manufacturing oils and heat treating quench oils. Although in the past, this contaminated wash water was discharged into the sewage system, it became necessary to haul the oil-contaminated wash water away to disposal sites or to treatment sites for further separation. Oily contamination in the parts washing solutions contributes to an inefficient cleaning process which typically requires secondary cleaning and manufacturing steps to correct, which then result in added time and expense. The contaminating oil in parts washers is often carried into subsequent heat treating tempering furnaces where the oil burns off as smoke in the plant which is then discharged into the local environment. Moreover, the presence of the oily contaminant also endangers the health and safety of the plant workers. Not only is the in-plant smoke a danger, but frequent changes of washing baths due to oil contamination require increased worker exposure to cleaning fluids and related handling hazards.
Several types of treatment methods and systems have been developed in efforts to efficiently separate oil from oil-water mixtures. Typically, these involve a means to remove a fraction of the mixture which is enriched in oil, and a means to further separate the oil from this fraction. The removal means are typically skimmers, which skim a fraction enriched in the oil from an oil-water mixture. Many different types of skimmers are known; these include belt skimmers, disk skimmers, drum/barrel skimmers, mop skimmers, tube skimmers, and floating suction skimmers. The separation means vary, and include from one to several of the following: filtration separation, gravity separation, including vertical and horizontal separators, and coalescing separators, which include tightly packed beds of plates, helical coalescers, and gas bubbles.
These treatment systems are utilized in a variety of situations, which range from open water to boat marinas to tanks in industrial plants. Although they vary in their details, they share several features in common: they are designed to be used for large volumes of oil-water mixtures with large surface areas, and to be used continuously. Thus, these systems are generally large, heavy, and relatively immobile as they are fixed in place, and then operated continuously.
However, there are many situation in which such large, immobile systems are less than ideal. Such situations include multiple small volumes of mixtures, each in small tanks, and tanks with obstacles protruding from the surface. Such obstacles include mechanical apparatus supporting the tank's purpose, including sprann and immersion hardware. In these situations, it would be desirable to collect and treat accumulated oil in the surface layer in batches, rather than continuously. It would also be desirable to have an oil-water mixture treatment system which is mobile, for use with multiple mixtures, as would exist in multiple tanks. It would also be desirable to have a collection means which is manually controlled, for maneuverability across a surface and around surface protruding obstacles in the oil-water mixture.